Retina & Vitreous
The optical portion of the eye, comprised of the cornea and the lens, focuses the image on the retina. The retina is the light-sensitive neural tissue which lines the inner surface of the eye like wallpaper and functions like an image sensor in a camera. The retinal cells are responsible for converting the light to signals which travel to the brain through the optic nerve.
The macula is the central part of the retina where the highest resolution of vision is obtained. In the center of the macula there is a tiny area called the fovea. The fovea is responsible for sharp central vision.
What are photoreceptors?
The photoreceptors are light-sensitive cells in the retina which are called rods and cones. The rods, which number 125 million in the human eye, cannot differentiate between colors. The cones, which number approximately seven million, are able to sense light as well differentiate colors. The vast majority of cones are located in the macula and in the fovea.
What is the vitreous?
The vitreous is a clear gel that fills the eye and permits light to pass from the lens to the retina. The vitreous has significant functions during the embryonic period. Following birth, the vitreous protects the lens from oxidative damage and the development of lens opacities (cataract). Removing the vitreous during surgery (vitrectomy) will gradually lead to the formation of a cataract.
What is Posterior Vitreous Detachment (PVD)?
①During the normal aging process, pockets of liquid appear centrally in the vitreous gel inside the eye.
This process is called vitreous syneresis.
②A certain time following syneresis, the posterior vitreous detaches from the back of the eye.
When posterior vitreous detachment (PVD) occurs, one may notice a floater in the visual field.
③The PVD may be accompanied by a vitreous hemorrhage. The hemorrhage may cause a decrease in
vision by obscuring the retina or the appearance of multiple floaters.
④A retinal tear develops in up to 48% of cases with vitreous hemorrhage.
The occurrence of PVD is age-related and is more common after the age of 50.
A posterior vitreous detachment without a hemorrhage may cause the retina to tear in 8-15% of the cases. The most common sign of a retinal tear is the sudden appearance of multiple floaters in the visual field.
A retinal tear may cause retinal detachment by allowing fluid from the vitreous cavity to enter the subretinal space.
The symptoms of retinal detachment are decreased vision or darkening of the visual field.
If a new retinal tear is diagnosed, it is generally treated with laser. Timely laser treatment will prevent the development of a retinal detachment in the vast majority of cases.
It is essential for anyone who has new or multiple floaters to have a comprehensive examination of the retina as soon as possible.
Retinal detachment is most often caused by a retinal tear that is formed due to traction of the anterior vitreous on the retina. Retinal detachment causes an impairment of nourishment of the retina, as the retina obtains oxygen and nutrition from a network of blood vessels (choroid) on the eye wall. Irreversible damage will occur if the retina is not reattached, making retinal detachment a pressing matter.
Methods of Retinal Detachment Repair:
During the scleral buckling operation, the surgeon sutures a soft silicone band (buckle) around the eye. The scleral buckle gently indents the external eye wall, relieving the retina from the internal traction forces of the vitreous. This procedure is typically indicated for young patients and in eyes without previous cataract surgery.
Vitrectomy is used to enable relief of the internal vitreous traction which caused the retinal detachment. Following reattachment of the retina, laser is used to treat the retinal tear/s and a special gas or silicone oil is placed in the eye to keep the retina attached until it recovers. Retinal detachments occurring following cataract surgery are usually treated with vitrectomy.
The highest primary success rates of retinal detachment repair are obtained either by scleral buckling or vitrectomy. In certain types of retinal detachments it is imperative to combine both scleral buckling and vitrectomy surgeries to achieve successful retinal reattachment.
Examples of Retinal Detachment Repair with Vitrectomy:
Videos are available in YouTube under eyemds.co.il.
Case description: A lady was diagnosed with retinal detachment due a peripheral retinal tear near the vitreous base. In addition, she had a macular hole. The presentation of a retinal detachment as a result of a retinal tear accompanied by a macular hole is rare and more complicated to repair.
Ocular Trauma with Retinal Detachment
Blunt ocular trauma may cause formation of a retinal tear and retinal detachment. The injury to the retina and adjacent ocular structures is proportional to the force of the trauma. Giant retinal tears are defined as tears spanning at least three clock hours of retina, and may be caused by substantial blunt injury of the eye.
Case description: A young boy was hit near the eye by a rock while playing with a friend. The injury caused extensive ocular trauma and the development of a giant retinal tear. Combined scleral buckling surgery and vitrectomy were performed during the repair.
Retinal Detachment due to Diabetes
Formations of membranes which pull and tear the retina may be a consequence of diabetes. This type of retinal detachment is not caused by posterior vitreous detachment.
Case description: A diabetic patient experienced a sharp decrease in her vision. Her eye developed membranes that caused a retinal tear which allowed fluid to travel under her macula. Several weeks after surgery, the central vision improved and the patient returned to her job as an English teacher.
Pneumatic Retinopexy (PR)
The procedure usually starts with cryogenic treatment of the eye wall (1) adjacent to the tear responsible for the detachment (2). An expanding gas bubble is injected into the vitreous cavity (3) followed by instructions designated for the patient to maintain specific head positioning (4). The gas bubble must be maintained under the tear (5), as it prevents fluid from entering the subretinal space for the period of the healing process (6). Due to patients' positioning boundaries, pneumatic retinopexy is generally used in cases of retinal detachment with breaks above the midline.
A decision regarding surgical treatment of macular conditions is reached by a host of considerations. The preoperative evaluations for macular surgery are performed in the clinic, and the treatment options are weighed and discussed. A careful decision is made to recommend the best treatment option for the individual patient and in some cases continued follow-up or medical therapy may be advised.
Macular surgery is performed to treat a number of conditions:
Treatment of submacular hemorrhage
Submacular hemorrhage may cause a substantial decrease in visual acuity unless well-timed treatment is implemented. The blood collects adjacent to an area with very high density of photoreceptors, and the iron found in the red blood cells causes irreversible damage to the photoreceptors. Injecting tissue plasminogen activator (t-PA) to the area of the hemorrhage helps to dissolve the blood clot and displace it away from the central retina.
Case description: A young myopic lady with one good eye experienced a sharp decrease in vision, and was admitted for surgery to displace a blood clot away from her macula. Several weeks following surgery, her visual acuity returned to her normal preoperative value.
Preparing for Surgery
You will be instructed by the surgeon about using your regular medications. If your operation will be performed under local anesthesia we recommend having a light breakfast. On the day of the operation you will need to bring to the medical center the results of your blood tests and ECG as well as a photo identification card. To help you relax before your surgery, you may take a mild sedative. The surgery itself usually takes 75 minutes, but you may be in the medical center for up to 3 hours due to the admission, preparation, and discharge procedures.
Once the surgery is over, we will patch the eye and you may go home. There is no need to stay in bed, and you may read, watch television, or listen to music. Strenuous physical activity is forbidden. Usually the recovery is relatively easy, but if you feel some discomfort we recommend taking an analgesic. The day after surgery we will remove your eye-patch, examine the eye, and give further instructions until your follow-up visit.